The present invention relates to a fuel cell and a fuel cell separator and, more particularly, to a technique effective in improving the efficiency of cooling of a fuel cell by means of a cooling medium.
For example, a solid polymer electrolyte type of fuel cell is constructed by stacking cells each formed of a membrane-electrode assembly (MEA) and separators. The MEA is constituted by an electrolyte membrane formed of an ion-exchange membrane, an electrode (anode) formed of a catalyst layer placed on one surface of the electrolyte membrane, and an electrode (cathode) formed of a catalyst layer placed on the other surface of the electrolyte membrane.
FIGS. 5 to 7 show separators 12a and 12b between which the MEA is sandwiched. Manifolds 43 and 53 for supplying and discharging cooling water are formed as rectangular openings through end portions of the separators 12a and 12b. Portions facing the electrodes of the MEA are formed, for example, by pressing to form a plurality of projecting ribs 13a in the front and back surfaces. Cooling water inflow channels 32a, main cooling water channels 32 and cooling water outflow channels 32b are formed between the ribs 13a. 
A plurality of unit cells constructed by sandwiching the MEA not shown in the figures between the separators 12a and 12b are stacked to construct a fuel cell stack. At this time, the main cooling water channels 32 and the cooling water inflow channels 32a and the cooling water outflow channels 32b communicating with the inlet and outlet sides of the main cooling water channels 32 are defined between one unit cell separator 12a and the other unit cell separator 12b in the adjacent pair of separators. Cooling water flowing in these channels 32a, 32, and 32b are sealed with a sealing member (gasket) 101c interposed between the two separators 12a and 12b, as shown in FIG. 6, and as disclosed in Japanese Patent Laid-Open Nos. 2002-231274 and 2003-157866.
During power generation from the fuel cell, cooling water supplied from the inlet-side manifold 43 flows through the channels 32a, 32, and 32b as indicated by arrow A, in FIGS. 5 and 7. The cooling water cools the portion (area) corresponding to the power generation region of the MEA (the region facing the electrodes of the MEA) and thereafter flows into the outlet-side manifold 53 to be discharged.